POTENTIATION BY NALOXONE OF PRESSOR REFLEXES

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Abstract
1 The effect of intravenous naloxone, an opiate antagonist, was studied on the pressor responses elicited by stimulation of afferent nerves (vagus and laryngeal superior nerves) in anaesthetized dogs 2 Although naloxone (0.1 mg/kgi.v.) alone failed to modify basic blood pressure, the pressor responses induced by stimulation of either the vagus or laryngeal nerve were potentiated by naloxone 3 Morphine (0.2mg/kgi.v.) suppressed these two cardiovascular responses. These depressor effects of morphine were reversed by subsequent injection of naloxone (0.1 mg/kg i.v.) 4 The results suggest the involvement of endogenous opiate peptides in pressor reflexes elicited by stimulation of the afferent nerves.